What is life: The long ascent from matter to mind

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Thomas R. Verny is a clinical psychiatrist, academic, award-winning author, poet and public speaker. He is the author of eight books, including the global bestseller The Secret Life of the Unborn Child and The Embodied Mind: Understanding the Mysteries of Cellular Memory, Consciousness and Our Bodies.

I watch Rufus, a friend’s dog, chew enthusiastically on a rubber bone. I know the dog is alive and his toy is not. I know that intuitively. But can I prove it scientifically? Can science parse the distinction between life and inert matter?

To be considered alive, does something have to be able to reproduce, move, grow, process energy? Any definition along these lines is riddled with exceptions. For instance, is a virus alive? While viruses do evolve, they don’t replicate on their own. They use the host’s tissues to make copies of themselves.

In Star Trek: The Next Generation, the definition of life as something that “absorbs compounds from its environment,” “excretes waste,” and “grows” is famously challenged by characters like Data to show its limitations. Fire or crystals, for example, also consume nutrients which is energy, “excrete” waste, and grow, yet are not considered alive.

Throughout Star Trek, the ultimate definition of life, particularly when discussing androids or artificial intelligence, often centres on sentience, consciousness, and self-awareness rather than just biological or metabolic functions. However, these are abstract concepts that are difficult if not impossible to define scientifically. The current challenge in biology is to formulate a cohesive conceptual framework for understanding what constitutes life and how it originated.

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Evolutionary biologists believe that organisms with cellular nuclei appeared around 1.8 billion to 2.7 billion years ago. Then there was the transition to multicellular organisms around 1.6 billion to 2 billion years ago, the abrupt diversification of body forms in the Cambrian explosion 540 million years ago, and the appearance of central nervous systems around 520 million years ago. [1]

The first anatomically modern humans, Homo sapiens, appeared in Africa around 300,000 years ago. [2] However, our earlier human ancestors, hominins, evolved in Africa much earlier, diverging from chimpanzee-like ancestors between 4 and 7 million years ago, [3] with early human species like Australopithecus (remember Lucy), living millions of years before that, around 3.2 million years ago. [4]

One of science’s most enduring riddles is how cells that metabolize, replicate and adapt emerged from matter that was once resolutely inert. Many prevailing accounts trace the story back to the early bombardment of earth by asteroids, events thought to have set in motion a cascade of chemical and environmental changes culminating in the appearance of the “last universal common ancestor,” or endearingly called, LUCA. [5,6].

Whether LUCA was a lone, hardy cell or a small community of primitive organisms remains an open question. What is clear is its legacy: every living thing on Earth today descends from it.

Estimates place LUCA’s existence around 4.2 billion years ago, some three hundred million years after the moon itself was born from a catastrophic collision between earth and a Mars-sized body. This was a violent, unsettled chapter in planetary history, marked by relentless impacts and extreme conditions. Before life could gain even the slightest foothold, earth likely required another hundred million years, perhaps two, to cool, stabilize, and become hospitable to biology. [7]

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In the last decades, major scientific breakthroughs across disciplines, from chemistry and biology to astrobiology, geology, the study of extreme environments, cosmology, quantum physics, and yes, even philosophy, have shed new light on the evolution and definition of life. Several recent international meetings have addressed these issues.

This past September at UC Berkeley, a conference titled Science & Philosophy: A Unified Pursuit? focused broadly on ultimate questions in science and philosophy, including the emergence and nature of life. I thought Luc Jaeger’s paper was particularly interesting.

Dr. Jaeger is professor in the Department of Chemistry and Biochemistry at the University of California at Santa Barbara. In his lab, RNA molecules are coaxed into forming tiny structures, molecular constructions that resemble Lego assemblies more than genetic code. This field, known as RNA nanotechnology, allows researchers to explore what RNA can do on its own, and how simple molecules might self-organize into increasingly complex systems.

RNA, a chemical cousin of DNA, occupies a curious dual role: it can store information and perform work. These experiments are not attempts to manufacture life, but to test plausible chemical steps by which life could have arisen naturally long before cells or brains existed. [8,9]

The following month, in Kyoto, Japan, the ALIFE 2025, Artificial Life Conference was held. The theme was “Ciphers of Life,” exploring information, computation, emergence, and what counts as life in artificial and natural systems.

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Mike Levin, a professor in biomedical engineering at Tufts University, was one of the many distinguished speakers. In his talk he emphasized the importance of acknowledging and, in fact, utilizing the goal directedness of life as a critical step in the maturation of the life sciences.

I asked him, over Zoom, how we would recognize novel forms of life beyond Earth, extra celestials?

His answer: “To be honest, I spend very little time thinking about the definition of life, per se. I don’t focus on life; I focus on cognition. If we sort of make a Venn diagram of all the things that are on the cognitive spectrum, and all the things that are live, how do those two sets interact? Right? I tend to think that cognition is the more important category, because I think there are many things that are probably not alive that nevertheless have cognition, and vice versa.”

His focus on agency in living systems seems to me closely related to the dominant theories about life on Star Trek. Kudos Star Trek.

The conference that particularly appealed to me was the Oxford 2026 Evolution Conference, last month. About 20 scholars and researchers spoke. One of the most outside-the-box papers was “BEEM: Biological Emergence-based Evolutionary Mechanism: How Species Direct Their Own Evolution,” presented by Raju Pookottil. Mr. Pookottil, an engineer and a self-taught evolutionary scientist, advanced the heretical idea that natural selection may not be the primary driver of adaptive evolution. Rather, he said, “Organisms may direct their own evolutionary trajectories.” [10]

In this view, organisms assess challenges, devise solutions, and transmit them across generations. Ants act as agents within colonies; complex protein networks perform analogous roles within cells. Genes, he argues, are tools rather than tyrants. Organisms can regulate gene expression and repair many accidental changes. Mutations, he suggests, are often not random and when they are, they are frequently corrected within a few generations. [10] Many studies show that mutations are uncommon, and in medicine, the mutations we notice most are often the harmful ones (disease and cancer). [11,12]

A growing body of research indicates that asteroids crashing to Earth may have sparked life here. [13] Evidence from missions such as NASA’s OSIRIS-REx and Japan’s Hayabusa2 support the idea that carbon-rich asteroids once harboured liquid water and water–rock reactions. [14, 15].

After impacting Earth, materials from asteroids may have undergone further transformation in hydrothermal settings before being transferred to surface environments where cycles of drying, re-wetting, and ultraviolet exposure concentrated them, packaged them into primitive membranes, and allowed rudimentary selection to occur. Life, according to this model, emerged not from a single privileged location but through a chemical relay, a gradual handoff from geology to protocells. [16, 17,18].

A substantial amount of ink and lately, electricity, has been spent by scholars in efforts to pin life down with a tidy definition. Metabolism, growth, and reproduction sound promising until one recalls that a candle flame manages all three yet remains adamantly unliving. [19].

Following a suggestion by Carl Sagan, NASA adopted a definition of life as “a self-sustaining chemical system capable of Darwinian evolution.” [20, 21] The word “system” was chosen deliberately, acknowledging that components of living systems – cells, viruses, even organisms – may not individually exemplify life in isolation. “Self-sustaining” was meant to exclude entities that require constant external intervention to exist. “Darwinian evolution” served as shorthand for replication with heritable variation and differential fitness. [22,23].

Living systems, in this context, differ from non-living ones by their use of free energy to produce and maintain order as part of a dissipative process. A dissipative process is an irreversible thermodynamic process that converts ordered, usable energy into disordered, unusable energy.

The prevailing view holds that life consists of reproduction with heritable variation. [24]. The transition from non-life to life was not a single event but a gradual process involving planetary habitability, prebiotic chemistry, molecular self-replication, self-assembly, and the emergence of membranes.

From the outset, this process required mechanisms that allowed molecules to change adaptively over time. This is where Mr. Pookottil’s contribution seems particularly valuable, as does his observation that mutations often lead not to progress but to dysfunction – birth defects and cancer rather than innovation.

Having studied genetics and epigenetics for the past 50 years, I believe that mutations propel evolution forward far less often than we have been led to believe.

There are many other processes responsible for the long ascent from matter to homo sapiens. Life emerged tentatively from non-living matter, very likely aided by asteroids striking a turbulent, chaotic Earth. What began as self-organizing molecules slowly acquired memory, agency, and, eventually, consciousness.

From the cacophony of the voiceless early Earth, over vast stretches of time and space, a few notes gradually arose, forming a melody played on various instruments in various combinations until it triumphed in a symphony: life.

References

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